Hi there, welcome to FitDay.
I have a couple of ideas. First, figure out what your trigger foods are...those that set you off and you know you will eat too much of. Try to eliminate those or avoid having them around as much as possible. Maybe it's something your husband can take your kids out for as a treat. Second, if you buy stuff for them that is not something you would want to be eating, try to get things you don't like, or flavors you don't like. I've also been known to ask my husband and son to hide their snacks if I don't feel I can keep out of them. You sound like you have a great family who would be willing to help, so maybe this is something they can do.
About meals, I don't think it really works to fix two separate things, one for you, one for them. It's too tempting to dive into the mac and cheese when you are sitting there looking at a salad. Instead, could you try eating what the family eats, with some modifications? For example, I make my guys tacos, but I eat the meat on a salad instead of shells or tortillas. If I make them mashed potatoes, I bake a sweet potato instead for me, but the rest of the meal is the same. To an extent, what's good for the goose is good for the gander, as one of our longtimers here used to say, so having them eat healthier is okay, but I understand it's hard to yank everyone's favorites away because you are wanting to lose weight. So moderation is the key. Also making healthier substitutes for things helps, like whole wheat pasta, brown rice, whole wheat bread.
They may also be able to gain a little bit by eating high calorie snacks...nuts, dried fruit, peanut butter, cheese.
Just one more thought...you mentioned that you bought everything low fat. In my opinion, that always backfires (and I say that from years of doing so myself). Low fat foods replace the fat with more sugar, more carbs, or chemicals, all of which cause weight gain. Your body needs fat...preferably healthy fat. It also needs protein and fiber.
At any rate, those are my thoughts. Hope some of them help, and I hope to see you around the boards!
"If you drop an egg, you don't say, 'Oh, shoot' and drop the other 11, do you?"
-Source unknown, but obviously brilliant
Reached goal 4/16/2010...but kind of afraid to look these days